Injector safety device

ABSTRACT

A safety member for use with an injection device is disclosed. The safety member includes a blocking ring extending into a housing of the injection device in blocking association with a latch member associated with a trigger mechanism of the injector, in which the blocking ring blocks movement of a portion of the trigger mechanism into a firing position. The safety member further includes a manipulable portion disposed outside the housing and configured for hand-manipulation by a user to remove the safety member from the housing to unblock the firing mechanism to enable firing of the injector.

FIELD OF THE INVENTION

The invention relates to injectors with safety devices, and moreparticularly to injectors with devices to help prevent inadvertentfiring.

BACKGROUND OF THE INVENTION

Various injection devices exist that use a form of an automatedmechanism to actuate injection of a liquid medicament into a patient.Examples of such devices include jet injectors, both needle-free andneedle-assisted, and autoinjectors. Although the precise mechanisms usedto complete injection can vary within and between these devices, mostinclude a feature within the injection mechanism that stores kineticenergy to be used to drive the injection mechanism during use. Further,many known injection mechanisms include a trigger mechanism to securethe device such that the kinetic energy remains stored until injectionis desired, whereby actuation of the trigger releases the injectionmechanism, allowing the stored kinetic energy drives the injectionmechanism to cause injection.

Examples of needle-free jet injectors are described in U.S. Pat. Nos.5,599,302; 5,062,830; and 4,790,824. These traditional injectorsadminister medication as a fine, high velocity jet delivered undersufficient pressure to enable the jet to pass through the skin. Thepressure used to deliver the medication is typically greater thanapproximately 4000 p.s.i. inside the compartment that contains themedicament in the injector. The injection mechanism in such needle-freejet injectors can be arranged to apply a force to a medicament storingchamber within the device such that the required pressure is createdwithin the chamber.

Self-injectors or autoinjectors like the ones disclosed in U.S. Pat.Nos. 4,553,962 and 4,378,015 and PCT Publications WO 95/29720 and WO97/14455 are constructed to inject medicament at a rate and in a mannersimilar to hand-operated hypodermic syringes. The self-injectors orautoinjectors have needles that are extended at the time of activationto penetrate the user's skin to deliver medicament through movement ofthe drug container and related needle. Thus the mechanism that providesthe force to deliver the medicament in self-injectors and autoinjectorsis also used to extend the needle and the drug container to cause theinsertion of the needle through the user's skin and then to apply aforce to a plunger movably disposed within the drug container to causethe medicament to be expelled from the container through the needle. Theautoinjectors manufactured, for example by Owen Mumford, thus use verylow pressures to inject the medicament, which is injected through aneedle in a relatively slow stream. The pressures applied in themedicament-containing compartments of this type of device are very low,reaching a maximum of around 60 p.s.i. and take around 5 to 10 secondsto inject 1 mL.

Additionally, needle-assisted jet injectors have been developed thatutilize a needle to initially penetrate the skin, most often to a depthless than that of a traditional hypodermic injector or autoinjectors.Once the skin is penetrated with the needle, the jet mechanism isactivated, causing the medicament containing liquid within the injectorto be pressurized and expelled through the needle and into the skin. Theinjection mechanism in needle-assisted jet injectors can be configuredto move the drug container and the needle to move forward to penetratethe skin and then exert the necessary injection force to a plungermoveably disposed within the container. Alternatively, the needle anddrug container can be properly positioned to penetrate the skin bybringing said needle and container to close proximity with the skinresulting in needle insertion while keeping the needle and drugcontainer in a stationary position and the injection mechanism can bestructured to pressurize the container. The pressure of the medicamentwithin the injector can be less than that of a traditional jet injector,because the tough outer layers of the skin have already been penetratedby the needle. Similarly, the pressure of the medicament is preferablyhigher than that of an auto injector or the like, causing the medicamentto penetrate the skin or the tissue below the skin to a depth that issufficient so that with the needle penetration and penetration themedicament remains substantially within the body. An additional benefitof the higher pressure exists in a faster time of injection resulting inless psychological trauma to the patient and decreasing the likelihoodof the user inadvertently terminating the injection prematurely byremoving the injector from the injection site.

Because of the stored kinetic energy associated with the trigger andinjection mechanisms, accidental firing can occur due to suddenmovements during shipping or due to mishandling of the device by a userincluding accidental actuation of the trigger mechanism. Accidentalfiring of the injection mechanism can cause the medicament to beexpelled from the device, which can be at a dangerously high pressure,depending on the type of injection device. Further, accidental firingcan cause an injection needle to move forward with respect to the devicewith sufficient force to penetrate the skin.

An injector is needed that provides a reduced risk of accidental firingduring shipping or handling thereof.

Additionally, many such injection devices are intended to be used asingle time only. Accordingly, a locking mechanism is desired thatprevents unintended repeated use thereof.

SUMMARY OF THE INVENTION

The present invention relates to an injector. The injector includes ahousing and a container portion disposed within the housing. Thecontainer defines a fluid chamber containing a medicament and includes aplunger moveably disposed therein that defines a portion of the fluidchamber. The injector also includes a firing mechanism including a ramaffixed to the plunger and extending axially therefrom and a latchmoveably disposed within the housing and configured to engage a portionof the ram. The injector further includes a trigger moveably disposedwithin the housing between a ready position wherein the latch is held inengagement with the portion of the ram and a firing position wherein thelatch is released, permitting movement of the ram. A safety member ispositionable relative to the housing so as to restrict movement of thetrigger into the firing position.

In one embodiment the housing can include an opening formed therein, andthe safety member can include a blocking member having an end disposedwithin the housing so as to abut a portion of the trigger. In such anembodiment the blocking member extends through the opening of thehousing and attaches to a body portion of the safety member that isdisposed outside of the housing.

In another embodiment, the injector can further include a guardextending distally of the housing that is retractable with respect tothe housing from a protecting position to an actuating position.Retraction to the actuating position can causes a portion of the guardto move the trigger into the firing position. In such an embodiment, thesafety member can restrict movement of the trigger mechanism into thefiring position by preventing movement of the guard into the actuatingposition. The safety member can include a blocking member and a bodyportion, the blocking member having an end disposed within the housingso as abut a portion of the guard. The blocking member can extendthrough an opening in the housing and into connection with the bodyportion, which is preferably disposed outside of the housing.Additionally or alternatively, the injector can include a sleeve affixedwithin the housing and configured for retaining the container, and thesafety member can include a locking element slidably associated with thesleeve so as to be moveable from a first position into a secondposition. In such an embodiment, the first position is such that theguard is retractable into the actuating position, and the secondposition is such that the locking element is positioned in a fixedrelationship to the sleeve and blocks movement of the guard into theactuating position. As a further addition or alternative safety membercan be in the form of a cap configured to cover an open end or the guardand to surround the guard. The guard can include a flange and the capcan include a projection such that a snap-fit is achieved between theguard and the cap with a portion of the cap abutting a portion of thehousing such that the cap restricts retraction of the guard into theactuating position.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the invention willbe apparent from a consideration of the following non-limiting detaileddescription considered in conjunction with the drawing figures, inwhich:

FIG. 1 is a side view of an injection device according to an embodimentof the present invention;

FIG. 2 is a cross-sectional view of the injection device of FIG. 1 in asafety state taken along line A-A;

FIG. 3 is an enlarged view of a portion of the cross-section shown inFIG. 2;

FIGS. 4A and 4B are perspective views of a safety member used inconnection with the injection device of FIG. 1;

FIG. 5 is a perspective view of an alternative safety member;

FIG. 6 is an additional cross-sectional view of the device of FIG. 1 inthe safety state;

FIG. 7A is a cross-sectional view of the injection device of FIG. 1 in aready state;

FIG. 7B is a cross-sectional view of the injection device of FIG. 1 atthe start of an injection state;

FIG. 7C is a cross-sectional view of the injection device of FIG. 1 atthe end of an injection state;

FIG. 7D is a cross-sectional view of the injection device of FIG. 1 at alocked state;

FIG. 8 is a perspective view of an injection device according to afurther alternative embodiment of the present invention;

FIG. 9 is a cross-sectional view of the injection device of FIG. 8;

FIG. 10 is a perspective view of an injection device according to afurther alternative embodiment of the present invention;

FIG. 11 is a cross-sectional view of the injection device of FIG. 10;

FIG. 12 is an exploded view of a portion of the trigger mechanismassociated with the injection device of FIG. 1;

FIG. 13 is a perspective view of a needle guard according to anembodiment of the injector of FIG. 1;

FIG. 14 is a cross-sectional view of the cap shown in FIG. 1; and

FIG. 15 is a graph showing the pressure within the liquid chamber of apreferred injection device as a function of time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a preferred embodiment of an injector 12 hasan outer housing 14 configured for allowing a user to handle theinjector 12. Outer housing 14 substantially contains most of thecomponents shown in FIG. 2. In an embodiment, outer housing 14 is formedfrom two mating portions 14 a, 14 b that can be configured to attach toone another by a snap or press fit or using adhesives, welding or thelike shown in FIG. 1.

Housing 14 includes a fluid chamber 22 therein that is configured forstoring and dispensing a liquid medicament. In the embodiment shown inFIGS. 1 and 2, fluid chamber 22 is formed in a prefilled syringe 18 thatfits within housing 14, but other types of fluid chambers can be used,including known types of medicament cartridges that can be prefilled,refillable, or the like. Additionally, fluid chamber 22 can beintegrally formed within housing 14. A safety member 80 is located onthe proximal end of outer housing 14 a and is removably affixed theretoby a plurality of tabs that extend through matching openings formed inouter housing 14 a to form a press-fit between safety member 80 andouter housing 14 a. It is noted that, in the context of this disclosure,the terms “proximal” and “distal” are used in reference to the positionof the device relative to a user of the device when held for injectionof a liquid medicament into a patient. Accordingly, a point locatedproximal to a second point would be closer to the user and vice versa.As discussed below, safety member 80 is configured to prevent or reducethe likelihood of unintended firing of the injection device during, forexample, shipping or handling of injector 12. Safety member 80 can beremoved by a user of injector to allow for substantially unrestricteduse of injector 12.

In a preferred embodiment sleeve 16 is housed within and mounted withthe housing 12 and acts as a syringe support member. The sleeve 16 isconfigured to hold and position a prefilled syringe 18 of the type knownin the art, such as the prefilled syringe commercially available underthe name BD Hypak™ from Becton, Dickinson and Company. In the preferredembodiment, sleeve 16 is substantially fixed to the housing 14, such asby snaps, an adhesive, a weld, or another known attachment. Theprefilled syringe 18 has a container portion 20 that defines in itsinterior a fluid chamber 22, which is prefilled with medicament to beinjected. At the distal end of the prefilled syringe 18 is aninjection-assisting needle 24. Needle 24 has an injecting tip 26configured as known in the art to penetrate the tissue of a patient,preferably the skin. A needle bore extends through the needle 24, asknown of the art. The bore is in fluid communication with the medicamentin the fluid chamber 22 and is open at the needle tip 26 to inject themedicament. The needle bore in the needle 24 affixed to the prefilledsyringe 18 is the only fluid communicating means at the distal end ofthe fluid chamber 22.

At a proximal side of the fluid chamber 22, opposite from the needle 24,is a plunger 28 that seals the medicament in the fluid chamber 22. Asyringe wall 30 preferably comprises a tubular portion, preferablycontaining the needle 24 at a distal end and open at a proximal end, todefine the fluid chamber 22. Plunger 28 is slideably received in thetubular portion. The prefilled syringe 20 is configured such that whenthe plunger 28 is displaced in a distal direction, the volume of thefluid chamber 22 is decreased, forcing the medicament out therefrom andthrough the bore of needle 24.

At the distal end of the fluid chamber 22 is a needle hub portion 32 towhich the needle is mounted. A syringe flange 35 extends radially,preferably from the proximal end of the syringe wall 30.

In the preferred embodiment, the syringe 18 has a syringe body 36 thatincludes the flange 35 wall 30 and hub portion 32 is of unitaryconstruction. A preferred material for the syringe body 36 is glass, butother materials can be used in other embodiments. A suitable prefilledsyringe is the BD Hypak™, which is available in various sizes andvolumes and can be prefilled with medicament. The glass of the syringebody is adhered to the needle with help of adhesives. Typicalmedicaments and medicament categories include epinephrine, atropine,sumatriptan, antibiotics, antidepressants, biologicals andanticoagulants. Using a prefilled syringe facilitates handling of themedicament when the injector is assembled, and there exists an extensivebody of knowledge surrounding injectable dosage forms in the prefilledsyringe as a small volume parenteral container.

To radially position the distal end of the prefilled syringe 18, sleeve16 preferably has a narrowed bore portion 51 that is preferablyconfigured to abut the outside of the syringe wall 30. The sleeve 16 canbe lined with a resilient material, such as an elastomer, or it can bemade unitarily with the rest of sleeve 16, such as by a series ofradially-aligned, resiliently-flexible fingers 53. The elastomer can beso configured to abut the syringe 18 flange 34 at the proximal end ofthe sleeve 16.

A firing mechanism is preferably also contained within housing 12 andconsists of a trigger 64 and a pair of resiliently deformable latches55. The firing mechanism also includes an inner housing 54 that can beattached to the outer housing 14, such as by snaps, an adhesive, a weld,or other known attachment. Latches 55 extend from the proximal end ofthe inner housing 54 and can be resiliently biased outwardly. Latchprotrusions 56 extend inwardly from the free ends of latches 55 and arereceived in a respective one of recess 58 formed in ram 60 in a blockingassociation therewith to prevent distal movement of the ram 60 prior tothe firing of the device. The ram 60 is urged toward the distal end ofthe injector 12 by an energy source, which preferably is a compressionspring 52, although other suitable energy sources can alternatively beused such as elastomer or compressed-gas springs, or a gas generator. Apreferred type of compression spring is a coil spring.

Trigger 64 is provided exterior to the inner housing to retain thelatches 55 in an inward position, thereby maintaining protrusions 56 inthe blocking association in the recesses 58 to hold ram 60 in theproximal position until firing is actuated. The trigger 64 is slideableinside outer housing 14 with respect to the latches 55, preferably in anaxial direction, and trigger 64 preferably surrounds the latch 54. In apreferred embodiment trigger 64 is free to move relative to outerhousing 14 and relative to outer housing and is only secured in place,after the removal of safety member 80, by the pressure exerted thereonby latches 55 and friction created thereby. Preferably, nothing ispresent that biases trigger 64 away from the proximal end of outerhousing 14, including springs or the like.

The injector 12 has a needle guard 66 that is moveable with respect tothe outer housing 14. The needle guard 66 is shown in FIGS. 2 and 7A ina protecting position, in which the needle 24 is disposed within theguard 66. Ridge 65 shown in FIG. 13 abuts an interior surface of outerhousing 14 so as to maintain needle guard 66 within housing 14 whenneedle guard is fully extended into the protecting position. The needleguard 66 is retractable, preferably into the outer housing 14, in aproximal direction to an injecting position, in which the needle tip 26and an end portion of the needle 24 are exposed as shown in FIGS. 7B and7C for insertion into a patient. In the preferred embodiment, theproximal movement of the guard is prevented substantially at theinjecting position.

The needle guard 66 is associated with the trigger 64 such that when theguard 66 is displaced proximally it slides the trigger 64 also in aproximal direction to release protrusions 56 from the recesses 58.Preferably, the trigger 64 has a latching portion 68 (FIG. 6) that abutsthe latches 55 in an association to bias and maintain the protrusions 56positioned in the blocking association with the ram 60 prior to thefiring of the device 12. When the trigger is slid proximately by theretracting of the guard 66 to the injecting position, the latchingportion 68 slides beyond the portion of latches 55 that it contacts toflex the latches 55 inward to maintain protrusions 56 into the recesses58 of the ram 60, allowing the protrusions 56 to move radially outwardlyfrom the recess 58 and therefore from the blocking association. Whenthis happens, spring 62 biases the ram 60 against plunger 28 to fire thejet injector.

Cap 110 is preferably affixable on the distal end of the device 12 so asto cover needle guard 66 and prevent accidental displacement thereofduring shipping or during handling prior to preparation for injection.Cap 110 can affix to the distal end of outer housing 14 by press-fit,screw fit or the like. In a preferred embodiment, cap 110 includes apair of projections 112 extending inwardly, as shown in FIG. 14, thatform a distally-facing ridge 114. In such an embodiment, needle guard 66is preferably formed with a pair of radially-extending flanges 67 thatare configured to abut the distal ridge 114 of projection 112 to securecap 110 to device 12. The upper edge 116 of cap 110 preferably abuts thedistal end of outer housing 14 such that distal surfaces 14 ofprojections 12 are held against flanges 67. This arrangement of the cap110 prevents compression of the needle guard 66 proximally into thehousing, as the cap 110 is juxtaposed between the guard 66 and housing,securing needle guard 66 in the protecting position to help preventaccidental firing of the injection mechanism.

Cap 110 can be removed from device 12 by twisting cap 110 relative tohousing 14 such that projections 112 are moved out of alignment withtabs 67, which allows the cap 110 to be moved distally away from needleguard 66. To prevent accidental removal of cap 110 from device 12 due toinadvertent twisting of cap 110, the cap preferably engages the housingand/or the guard to require an initially elevated force, such asrequiring the cap to snap away from its closed position beforecompleting the rotation to remove the cap. For example, upper edge 116of cap 110 is preferably inclined, as shown in FIG. 14. The incline caninclude a curve, as shown, but generally the edge 116 should have oneedge 118 that is higher than the other edge 120. The distal end of outerhousing 14 preferably has a profile that matches that of upper edge 16of cap 110. This arrangement requires deflection of cap 110 to allow fortwisting thereof and increases the force necessary to cause cap 110 totwist relative to needle guard 66. In an alternative embodiment, the caphas a threaded or cammed association with the tabs 67, or can haveanother arrangement therewith so that the cap is removed by rotating.

Cap 110 is preferably attached to device 12 during assembly thereof.This can be done by properly aligning cap 110 and twisting it relativeto needle guard 66 while applying a proximally-directed force theretosuch that projections 112 move behind flanges 67. Alternatively, flanges67 can be structured to be deflectable inwardly by disposing them on acorresponding tab 69 formed on needle guard 66. In such an embodiment,cap 110 can be assembled onto needle guard 66 prior to assembly ofspring 72 thereinto, as spring 72 can interfere with the inwarddeflection of tabs 96. Alternatively, cap 110 can be resilientlydeformable to allow cap 110 to be pressed onto needle guard 66 such thatprojections 112 pass over flanges 67.

The guard 66 is preferably resiliently biased distally towards theprotecting position by compression coil spring 72. Also, the needleguard 66 has an axial opening 74 to allow the needle 24 pass therethrough, and which may be sized according to the type of injectordesired. The construction of the present embodiment allows a user topush the distal end of the injector 12 against the patient's skin,pushing the needle 24 into the skin at an insertion location,substantially at the same speed as the injector is pushed. Once theneedle 24 is fully inserted to an insertion point at a penetrationdepth, the trigger mechanism fires the jet injection to an injectionsite.

In the preferred embodiment, such as for subcutaneous injection using aneedle-assisted jet injector, the guard 66 is configured to allowinsertion of the needle to a penetration depth in the skin that is up toabout 5 mm below the skin surface. More preferably, the penetrationdepth is less than about 4 mm, and in one embodiment is less than about3 mm. Preferably, the insertion depth is at least about 0.5 mm and morepreferably at least about 1 mm. In another embodiment, the distance 76by which the needle extends past the guard 66 or the distal surface ofthe guard 66 that contacts the skin is up to about 5 mm, more preferablyup to about 4 mm, and in one embodiment up to about 3 mm. Preferably,extension distance 76 is at least about 0.5 mm, more preferably at leastabout 1 mm, and most preferably at least about 2 mm. In a preferredembodiment, tip 26 extends by a distance 76 of around 2.5 mm beyond theportion of the guard 66 that contacts the skin in the injectingposition.

In another embodiment, such as for intramuscular injection using aneedle-assisted jet injector, the injector is configured to allow theneedle to be inserted into the patient to a penetration depth in theskin, or alternatively beyond the distal surface of the guard, by adistance of up to about 15 mm. In one embodiment, this distance is aboutbetween 10 mm and 14 mm. Other exposed needle lengths can be selectedfor jet injection to different depths below the skin, with a preferredoverall penetration length of between about 0.5 mm and about 20 mm. Inthese embodiments, the needle guard is preferably configured forretracting from a protecting position, preferably covering the entireneedle, to an injecting position, in which the desired length of the endof the needle is exposed.

As mentioned previously, safety member 80 is removably affixed to thedistal end of outer housing 14. Safety member 80 includes a body portion84 and a pair of resiliently-flexible legs 82 extending therefrom. Inthe embodiment shown, legs 82 are configured to extend intocorresponding holes or slots 15 (FIG. 4A) formed in the proximal surfaceof outer housing. Legs 82 are shaped to provide a pressure fit withinslots 15 to retain safety member 80 on housing 14. Legs 82 arepreferably biased outwardly and can further include tabs 86 disposed outthe outside surfaces thereof to engage the inside of outer housing 14 atthe location of slots 15 to further the retention of safety member 80onto outer housing 14. Legs 82 are further preferably shaped to allow auser to remove safety member from outer housing 14, when injection isdesired. Legs 82 should, however, prevent safety member 80 from becomingaccidentally or unintentionally dislodged from its attachment to outerhousing 14.

Legs 82 are further configured to abut the proximal-most surface of thetrigger 64, preferably the latching portion 68. The abutment of legs 82against latching portion 68 preferably hinders or prevents jostling orother motion of trigger 64 in the proximal direction, which would causethe injection mechanism to fire. In an embodiment, it is possible tocause safety member 80 to become dislodged from outer housing 14 byforced proximal movement of guard 66, causing latching portion 64 topush proximally on legs 82 such that they are pushed out of the slots inwhich they are received. Legs 82, however, are preferably configured inrelationship to housing 14 and the firing mechanism such that the forcenecessary for latching portion 68 to force legs 82 out of slots 15 issufficient to prevent trigger 64 from being jostled out of position dueto vibration during shipping or from acute shock during shipping orhandling caused by dropping of device 12. Further preferably, safetymember is preferably configured to require a force of between 1 and 10lbs applied, for example, by the user of the device for removal thereoffrom the outer housing 14. In a preferred embodiment, between about 2.5and about 5 lbs of force is required for removal of safety member 80from outer housing 14.

An alternative embodiment of safety member 180 is shown in FIG. 5. Inthis embodiment, body portion 184 forms an elongated tab 188 thatextends along the outside of outer housing 14. The end of tab 188includes a projection 189 that is configured to fit within acorresponding opening 187 formed within outer housing 14. In thisembodiment, the interaction between projection 189 and the correspondingopening 187 further secures safety member 180 to outer housing, furtherpreventing safety member 180 from becoming unintentionally dislodgedfrom housing 114 b. Safety member 180 is preferably configured such thatelongated tab 188 is of an appropriate length to extend through itsproperly-positioned corresponding opening 187 and into the interior ofouter housing 114 to a position that is proximal of guard 66, and distalof trigger 64. Such an arrangement blocks movement of guard 66 such thatit is prevented from moving proximally and into contact with trigger 64upon an unintentional or accidental force being applied to guard 64.

In an alternative embodiment of injector 134, shown in FIGS. 8 and 9, asafety member 136 is included that has an outer, manipulablehandling-portion 138, a catch member 140, and a blocking ring 142. Thecatch and blocking rings 140,142 are received in a safety opening 144 inthe proximal portion of the housing 146, preferably extending radiallyfrom the handling portion 138, which is disposed outside the injectorhousing 146.

In the arrangement shown, the safety member 136 is in a safety position,associated with the injector 134 with the blocking ring 142 in ablocking association with the trigger 148. In the safety position, theblocking ring 142 blocks accidental movement of the trigger 148 in aproximal, axial direction, which movement would cause the release oflatch protrusions 56 from the recess 58 of ram 150, allowing spring 152to bias the ram 150 to fire the injection. The trigger 148 is preferablybell-shaped, which provides additional proximal, axial surface to abutand be blocked by the blocking ring 142 in the blocking position.

In this embodiment, without the safety member 136 in the safetyposition, the trigger 148 could accidentally slide proximally, such asdue to a shock or vibration, and cause the injector to fireunintentionally. Also, without the safety member 136 in the safetyposition, accidental depression of the guard 66 would move the trigger148 proximally, causing the injector 134 to fire.

The catch member 140 preferably has an enlarged or curved tip 154 toprovide a snap fit with the injector housing 146 to retain the safetymember 136 in the engaged in the safety position with the injectorhousing 146 and prevent or inhibit accidental dislodging of the safetymember 136 from the safety opening 144. The preferred catch member 140is resiliently flexible, and sufficiently pliant to enable removal ofthe safety member 136 from the injector housing 146 by grasping andpulling the handling portion 138 with a user's finger tips, beforeintentionally firing the injector 134.

Referring to FIGS. 10 and 11, injector 156 includes a safety member 158with a flexible body 160, which is preferably resiliently flexible andextends circumferentially around the exterior of the injector housing146. The safety member 158 has a free tail 164 that is preferably angledaway from the housing 146 in the safety position shown, to facilitatepushing the tail 164 up over the proximal side of the injector 156 witha user's fingers to disengage and remove the safety member 158 from theinjector housing 146.

A blocking ring 162 of the safety member 158 is received in safetyopening 144. In the safety position, blocking ring 162 is in a blockingassociation with trigger 148 to block movement of the trigger 148 in aproximal, axial direction to prevent inadvertent firing of the injector,as described above.

The safety members described herein can be used with other types ofinjectors, including needle-assisted jet-injectors that do not employprefilled syringes, with needle-free injectors, and with other types ofpowered injectors. Jet injectors especially benefit from this safetymechanism due to the power of their injection when fired, even whenfired inadvertently. The safety members 80,136,158 are preferably madeof a unitary piece, such as of a resilient plastic or metal, althoughother suitable constructions and materials can be used.

In the preferred embodiment of a needle-assisted jet injector, thespring 62 and the prefilled syringe 18 are configured to jet inject themedicament. Thus, the spring 62 applies a force on the plunger 28 thatis sufficient to elevate the pressure within the fluid chamber 22 to alevel high enough to eject the medicament from the needle 24 as a jet.Jet injection is to be understood as an injection with sufficientvelocity and force to disperse the medicament to locations remote fromthe needle tip 26 and thus minimize leakback at the injection site.

The graph shown in FIG. 15 shows a pressure-profile over time for afiring mechanism associated with an exemplary type of injector withwitch the presently-disclosed safety devices can be used. While thepressure profile shown is of the type typically associated with jetinjection, a person of ordinary skill in the art would understand thatthe various embodiments of the invention disclosed herein are notlimited, however, to jet injection, but would also be useful, forexample, with other types of injection utilizing stored kinetic energy.Referring to the graph shown in FIG. 15, numeral 288 represents thepoint in time when a preferred embodiment of device 12 is fired, andnumeral 290 represents the point of completion of the medicamentinjection, preferably when the plunger 28 hits the forward wall of thecontainer portion 220. Numeral 292 represents the initial and peakpressure during the injection, and numeral 294 represents the final andlow pressure during the injection. Because the spring 62 of thepreferred embodiment has a linear spring constant and aninjection-assisting needle is used to puncture the skin beforecommencing the injection, the pressure drops substantially linearly fromthe start of the injection 288 until the injection is completed. Thefinal pressure 294 at the end 290 of the injection is sufficientlyelevated so that even at the end of the firing stroke of ram 60, themedicament is still jet injected, and a very small amount or none of themedicament is deposited in a bolus around the needle tip 26.

Preferably the peak pressure during the injection, using the preferredneedle-assisted jet injector, is less than about 1,000 p.s.i., morepreferably less than 500 p.s.i., and most preferably less than about 350p.s.i. At the end 80 of the injection, the pressure 84 applied to themedicament in the fluid chamber 22 is preferably at least about 80p.s.i., more preferably at least about 90 p.s.i., and most preferably atleast about 100 p.s.i. In one embodiment of the invention, the initialpressure 82 is around 330 p.s.i., and the final pressure is about 180p.s.i., while in another embodiment the initial pressure 292 is about300 p.s.i., dropping to around 110 p.s.i, at the end 284 of theinjection. Other injection rates are used for other embodimentsdiscussed herein. For example, needle-free jet injectors can use aninjection pressure in the range of about 4,000 p.s.i. or greater.Furthermore, autoinjectors can use an injection pressure in the range ofabout 60 p.s.i. or less. The needles used in the preferred embodiment isbetween 26 and 28 gauge, and are most preferably around 27 gauge, butalternatively other needle gages can be used where the other componentsare cooperatively configured to produce the desired injection.Preferably, the components of the injector 12 are configured to jetinject the medicament to a subterraneous injection site.

The amount of medicament contained and injected from fluid chamber 22 ispreferably between about 0.02 mL and 4 mL, and preferably less thanabout 3 mL, and in the preferred embodiment is around 1 mL. Largervolumes may also be selected depending on the particular medicament anddosage required. Preferably, the prefilled syringe is assembled into theremaining parts of the jet injector 12 already containing the desiredamount of medicament. In a preferred embodiment, the prefilled syringecontains about 1 mL of medicament.

Preferred injection rates are below about 1.0 mL/sec., more preferablybelow about 0.8 mL/sec., and preferably at least about 0.4 mL/sec., morepreferably at least about 0.5 mL/sec, and most preferably between about0.60 and about 0.75 mL/sec. Preferably, the injection of the entireamount of medicament is completed in less than about 2 seconds, morepreferably in less than about 1.5 seconds, and most preferably in lessthan about 1 seconds. Preferably, the medicament injection takes atleast about 0.5 second, and more preferably at least 0.6 seconds. Apreferred embodiment injects the medicament at about 0.67 mL/sec.,completing the injection of 0.5 mL in about 0.75 seconds. Otherinjection rates however, are possible for the alternative embodiments ofdevice 12 discussed herein.

U.S. Pat. No. 6,391,003 discloses several experimental results ofpressures that can be applied to medicament in a glass cartridge, using26 and 27 gage needles. The following table illustrates exemplaryinjections with different peak pressures that can be used with glassprefilled syringes:

Pressure and Time (sec.) to Inject 1 cc Pressure 26 Gauge needle 27Gauge needle 150 p.s.i. 2.1 4.2 200 p.s.i. 1.9 3.9 240 p.s.i. 1.7 3.3375 p.s.i. 1.4 3.1

It is foreseen that higher pressures and flow rates will be used withshorter needle penetration into the patient skin to achieve jetinjections to a particular desired depth substantially withoutmedicament leakback. Alternative embodiments can use higher or lowerinjection pressures. For instance, needle-free injectors will typicallyuse higher pressures to penetrate the skin without a needle, andautoinjectors will use lower pressures to simulate a hand-poweredsyringe injection.

It has been found that using the needle-assisted jet injection of thepreferred embodiment, short needles can be used to inject medicament todifferent parts of the skin, preferably subcutaneously, substantiallywithout any leakback. Using a needle that extends by about 2.5 mm fromthe needle guard 66, a 27 gauge needle 24, and a pressure in the fluidchamber 22 peaking at around 300 p.s.i. and ending at around 100 p.s.i.,resulting in a flow rate of about 0.5 mL/sec., 1 mL of medicament hasbeen found to successfully be injected without leakback in close to 100%of the tested injections. Thus, the needle-assisted jet injector of thepresent invention permits jet injection of the medicament using a veryshort needle reliably regardless of the thickness of the patient's skinor the patient's age, weight or other factors.

In a preferred embodiment, device 12 includes a locking element, such asa locking ring 70 associated with the injection mechanism. As shown inFIGS. 7A-7D, locking ring 70 is preferably disposed between sleeve 16and needle guard 66, and interacts with sleeve 16 and needle guard 66such that locking ring permits needle guard 66 to move relative to outerhousing 14 through a single injection cycle. This includes movement fromthe protecting position (FIG. 7A) into the injecting position (FIGS. 7B,7C) and then to return to the protecting position (FIG. 7D) under theforce of compression spring 72 once injection is complete. When needleguard 16 returns to the protecting position at the end of the injectioncycle, locking ring is positioned relative to sleeve 16 and needle guard66 such that further movement therebetween is restricted.

As shown in FIGS. 7A-7D, movement of needle guard 66 through one lockingcycle causes locking ring 70 to move relative to sleeve 16 from aninjecting position to a locking position. In the injecting positionlocking ring 70 is disposed such that the upper arms 71 of locking ring70 engage a portion of the device that is associated with the medicamentchamber, such as proximal notches 92 formed in the outer surface ofsleeve 16. The engagement of upper arms 71 within proximal notches 92releasably maintains locking ring 70 in the injecting position. As shownin FIG. 12, locking ring 70 can be generally annular in shape so as tosurround the medicament chamber, either directly or indirectly such asby surrounding sleeve 16. Locking ring 70 further includes a pair oflower arms 73, each having a tab 74 formed on the end thereof. Whenlocking ring is in the injecting position, tabs 74 are received in slot95 formed in needle guard 66 such that needle guard is slideable througha predetermined distance over locking ring 70. As needle guard 66 ismoved into the injecting position with respect to outer housing 14,needle guard 66 slides over locking ring 70 such that tabs 74 reach theend of slot 95 and are depressed inwardly, allowing needle guard 66 tocontinue to move into the injecting position. When the injectingposition is reached, tabs 74 align with holes 96 of needle guard 66,allowing lower arms 73 to return to their natural position, wherein theupper surfaces of tabs 74 engage an edge of the holes 96, therebycoupling locking ring 70 to needle guard 66.

As needle guard 66 returns to the protecting position, needle guard 66pulls distally on locking ring 70, causing upper arms 71 to release fromproximal notches 92. Preferably, upper arms 71 and proximal notches 92are formed with mating inclined surfaces such that the inclined surfacesof upper arms 71 engage another portion of the device that is associatedwith the medicament chamber, such as by extending into proximal notches92 but are forced outwardly by distally-directed movement relativethereto. This configuration allows the needle guard 66 to cause lockingring 70 to move therewith and out of the injecting position as needleguard moves distally toward the protecting position over sleeve 16,which remains stationary.

When needle guard 66 reaches the protecting position, upper arms 71 moveover distal notches 93 formed in sleeve 16 such that the upper surfaces75 of upper arms 71 engage the upper surface 94 of distal notches 93.Further, in such a position, flange 77 of locking ring 70 abuts surface67 of needle guard to block needle guard 66 from distal motion relativeto locking ring 70. This engagement prevents locking ring from movingproximally with respect to sleeve 16. Because locking ring 72 is coupledto needle guard 66, and because sleeve 16 is attached to outer housing,needle guard 66 is locked relative to outer housing 14, and is preventedfrom being moved back into the injecting position. This prevents needle24 from being accidentally exposed after use of device 12.

All of the references specifically identified in the detaileddescription section of the present application are expresslyincorporated herein in their entirety by reference thereto. The term“about,” as used herein, should generally be understood to refer to boththe corresponding number and a range of numbers. Moreover, all numericalranges herein should be understood to include each whole integer withinthe range.

While illustrative embodiments of the invention are disclosed herein, itwill be appreciated that numerous modifications and other embodimentsmay be devised by those skilled in the art. For example, the featuresfor the various embodiments can be used in other embodiments. In analternative embodiment, the hosing can be fixed to the bracket, and theinner portion, defining at least the bottom of the chutes can slide inand out of the housing. Therefore, it will be understood that theappended claims are intended to cover all such modifications andembodiments that come within the spirit and scope of the presentinvention.

1. An injector, comprising: a housing; a container portion disposedwithin the housing, defining a fluid chamber containing a medicament,and including a plunger moveably disposed therein and defining a portionof the fluid chamber; a firing mechanism including a ram affixed to theplunger and extending axially therefrom; a latch moveably disposedwithin the housing and configured to engage a portion of the ram; atrigger moveably disposed within the housing between a ready positionwherein the latch is held in engagement with the portion of the ram anda firing position wherein the latch is released, permitting movement ofthe ram; and a safety member that is positionable relative to thehousing so as to restrict movement of the trigger into the firingposition; and, a guard extending distally of the housing, the guardbeing retractable with respect to the housing from a protecting positionto an actuating position, wherein retraction to the actuating positioncauses a portion of the guard to move the trigger into the firingposition, wherein the safety member restricts movement of the triggermechanism into the firing position by preventing movement of the guardinto the actuating position.
 2. The injector of claim 1, wherein thehousing includes an opening formed therein, and wherein the safetymember includes a blocking member having an end disposed within thehousing so as to abut a portion of the trigger, the blocking memberextending through the opening of the housing and attaching to a bodyportion of the safety member that is disposed outside of the housing. 3.The injector of claim 2, wherein the blocking member is retained withinthe opening in the housing by a snap fit and is configured to be removedby a user to permit movement of the trigger into the firing position. 4.The injector of claim 2, wherein the trigger is moveable from the readyposition to the firing position by a force in a first amount, andwherein a frictional relationship is present between the trigger and thelatch creating a retaining force between the trigger and the latch in asecond amount, and wherein the safety member restricts the movement ofthe trigger into the firing position by providing a safety force to thetrigger in a third amount such that the first amount is greater than thesecond amount by about 2.5 lbs.
 5. The injector of claim 2, wherein thelatch includes a flexible arm and a projection, wherein the ram includesan indentation, wherein the projection is receivable within theindentation, and wherein the projection is held within the indentationwhen the trigger abuts the latch in the ready position.
 6. The injectorof claim 5, wherein the indentation and the projection are configuredsuch that the latch restricts movement of the ram when the projection isheld in the indentation by the trigger and such that movement of thetrigger into the firing position allows the projection and theindentation to disengage and the ram to move axially relative to thelatch.
 7. (canceled)
 8. The injector of claim 1 further including aneedle having a tip and being associated with the chamber forpenetrating the skin of a patient for injection of the medicament,wherein the guard has a distal end that is positioned distally of theneedle tip when the guard is in the protecting position, and wherein thedistal end of the guard is positioned proximally of the needle tip whenthe guard is in the retracted position.
 9. The injector of claim 1,wherein the housing includes an opening and wherein the safety memberincludes a blocking member and a body portion, the blocking memberhaving an end disposed within the housing so as to abut a portion of theguard, the blocking member extending through the opening in the housingand into connection with the body portion, and wherein the body portionis disposed outside of the housing.
 10. The injector of claim 9, whereinthe guard includes a proximal end and wherein the trigger includes adistal end, wherein the proximal end of the guard is disposed axiallyremote from the distal end of the trigger when the guard is in theguarding position, and wherein the blocking member is disposed axiallybetween the proximal end of the guard and the distal end of the trigger.11. The injector of claim 1, wherein the injector includes a sleeveaffixed within the housing and configured for retaining the container,and wherein the safety member includes a locking element slidablyassociated with the sleeve so as to be moveable from a first positioninto a second position, wherein the first position is such that theguard is retractable into the actuating position, and wherein in thesecond position the locking element is positioned in a fixedrelationship to the sleeve and blocks movement of the guard into theactuating position.
 12. The injector of claim 11 further including aspring positioned within the housing to resiliently bias the guardtoward the protecting position such that subsequent to retraction of theguard into the actuating position, the guard returns to the protectingposition, wherein the retraction of the guard engages the guard with thelocking member, and wherein the subsequent return of the guard to theprotecting position moves the locking element into the second position.13. The injector of claim 1, wherein the safety member is in the form ofa cap configured to cover an open end of or the guard and to surroundthe guard, wherein the guard includes a flange and the cap includes aprojection such that a snap-fit is achieved between the guard and thecap, a portion of the cap abutting a portion of the housing such thatthe cap restricts retraction of the guard into the actuating position.